Gravity meter



June 20, A. GRAF GRAVITY METER `Filed Feb. 4, 1941 #www I Patented June20, 1944 Anton Graf, Berlin-Steglitz, Germany; vested in A the AlienProperty Custodian Application February 4, 1941,l Serial No. 377,395

In Germany December 30, 1939 Claims.

It has previously been proposed to constructv gravity meters in whichthe displacement caused by variationsin gravity of an elasticallysupported mass serves to control the exposure of .photo-cells arrangedin differential connection.

In such optic-electric gravity meters a preferably perforated diaphragmcapable ,of being displaced together with the mass is displaced relativeto a fixed diaphragm, by which means the' A exposure of a photo-cellsystentis varied so that the difference between the photo-cell currents(voltages) is a measure of the mass displacement and the gravityvariation, respectively. The present invention relates to theconstructive development of such an instrument for rendering it suitablefor field use.

Oneof the principal considerations in the construction of suchinstruments is that of minimizing any temperature influence from theheat producing sources of light upon the extremely temperature-sensitiveparts of the instrument,

i. e. the photo-cells and the suspension spring.

` According to the invention such protection against temperatureiniiuences is facilitated by arranging the photo-cells back to back inthe interior of the instrument so as to be capable of exposure tosources of light arranged outside of said instrument.

(Cl. 26S-1.4)

mined by the perforation and the source of light. Such a relativedisplacement into the normal to said plane may however take place alsoat an inclination of the instrument and thus falsify the measurement.Hence it must be rendered possible to align by adjustment themovablediaphragms in all directions in such a Way that an inclination of theinstrument does not result in a displacement of the movablediaphragminto the normal to the plane determined by the perforation andthe source of light. The proper position of the movable diaphragm mostadequately fulfilling this condition cannot be previously determined buthas to be ascertained in practicev by means of adjustment. In order toprovide such universal adjustment of the movable diaphragms it isadvantageous to connect the diaphragms rigidly with the mass and to fixthe mass at a clamping member at any desired inclination to the springaxis, said clamping member being arranged at one end of the suspensionspring. Such an arrangement is constructionally much simpler than thatof having the diaphragms fixed to the mass so as to be universallyadjustable, although in principle this may serve equally well. A furtherpossibility of adjustment may beprovided by arranging the sources oflight so as to A further point to be considered is, however.

that the photo-cells in the interior of the instrument, and particularlythe diaphragms between these and the sources of light, are easily andaccurately adjustable. For this purpose they are arranged in such mannerthat a perforated diaphragm each is secured so as to be turnable andvertically displaceable in front of eachphoto-cell, asimilarly-perforated second diaphragm being suspended in front of saidfirst diaphragms.

The mounting of the inner diaphragm may in `this connection. be firmlyconnected with that of Y the respective photo-cell and is preferablyguided in a recesspf a slide gliding in turn in a vertical guide ofaframe-like support. In this way it is possible to adjust the fixeddiaphragm by means of turning and vertical displacement into a desiredposition relative to the diaphragm secured on the mass, and moreparticularly to alignthe two diaphragms.

be adjustable vertically relative to the first diaphragms. By venticaldisplacement of the incandescent lamp the plane determined by thesourceof light and the diaphragms may be displaced and more easily alignedwhen movements of the movable diaphragms occur due to an inclination ofthe instrument.

An embodiment of the invention is described in the following.' referencebeing had to the accompanying drawing representing a vertical sectionthrough the instrument.

vIn a casing I there is suspended by a spiral spring 2 a mass 3 of agravity meter. Said mass is fixed to the spring 2 by means of a mountingappliancev 4 possessing a spherical surface 5 serv- It is, however,necessary likewise to provide for the possibility of adjusting themovable dia-- phragms, as will be seen from the following. Theinstruments are constructed so as to indicate a measuring value when theparallel adjusted diaphragms are displaced relative to one another ining as support for the mass 3. By means of four adjusting screws 6 themass 3 may be mounted so as to be universallyinclined relative to thespring axis. A support' 'I is inserted in the casing I, two frames 9, 29being fixed on said support by means of screws 8. Two further frames.10, 30 are slidably arranged in vertical guides in the frames 9,'29,respectively, the frames lll, 30

' serving as supports for the photo-cells Il, 3|, re-

the plane which is normal to the plane deter.-

spectively. Said photo-cells are arranged back tol back with theirlight-sensitive front part turned outwardly. They are arranged in aseries addi' tivecnnection and are in communication with a galvanometer35. In front of each photo-cell there are disposed-in respectiverecesses I3, 33

` of the'slides I0, 30 carrying the photo-cells I I, 3I,

respectively-diaphragms I2, 32, respectively, and in such manner as tobe turnable in the respective slides-I0, 30 as well as displaceable inthe respective frames 9, 29. Screws Il serve to Two small pot-shapedcasings I8, 23 having flanges are screwed on to the sides of the casingI, the surface of said cases being increased by cooling ribs I9. Sourcesof light 20, 2li, respectively, are screwed on to the inner bottoms ofsaid cup-shaped casings I3, 28. 'I'he screws serving to x said sourcesof light are arranged in slots 22 so as to allow for a verticaldisplacement of said sources of light. The casing I possesses windows 23permitting the passage of rays of light. Said windows are provided withheat protecting glass plates 2|, 34 for shutting oil' the interior ofthe casing I from the respective chambers of the lamp casings I3, 23.

The mode of operation of a gravity meter according to the invention isdescribed in the following. Upon a displacement of the mass A3 thediaphragms I1, 21, respectively, rigidly connected therewith aredisplaced along'with it relative to a measure of the displacement of themass 3 and therefore of the force of gravity.'

As the displacements to be determined in this way are exceedingly small,it is essential to reduce as much as possiblethe possibility of thediaphragms, photo-cells and especially the spring' from being inuencedby temperature conditions.

To this endthe heating` eilect of the lamps 2-, 2l arranged outside thecasing I is diverted .by means of the cooling ribs I9. In addition thecirculation of heated air in the interior of thecasing I is preventedbythe windows 23, 23, the glass 2l, 24 of which is of a non-conducting.kind as regards heat.

'I'he photo-cells Il, I2 and 32, respectively, are adjusted bydisplacing the respective diaphragms I2 and 32 relative to therespective lamps 2l, 23. I'he vertical position of the diaphragms I1 and21 corresponds to the zero position of the-mass 3. The inner dia'-phragms I2,. 32, respectively, are shifted into the position requiredfor producing a diilerential efrelative to the respective diaphragms I2,32 as the mass is pendulously suspended. Such a displacement, however,must not be permitted to cause variations in the exposure of thephoto-cells I I, 3|, i. e. to simulate a displacement of the mass 3 asbeing due to differences in gravity. To this end the perforation is notarranged rectilinearly but in circular arcs, the center of these arcsbeing the fictitious pivot point of the pendulously susinclination. Thiscan only be achieved by enthe diaphragmsU I2, 32, flxedly arranged inthe casing I.

3| and the diaphragms fect by vertical displacement of the respectiveslides I0, 30 in the frames 9. 29. Inorder to eilect parallel adjustmentof the diaphragms, the inner diaphragms I2, 32 are turned inthe-respective recesses I3, 3 3 in the slides Il, 39.

Additional appliances are further provided for eliminating th'e inuencesexerted on the measuring operations by inclinations of the instrument.

At an inclination of the casing I the diaphragms I'I, 21 rigidly ilxedon the mass 3 are disirlacedl suring that the movable diaphragms I1, 21at a displacement of the mass 3 due to inclination of the casing I if atall possibledo not move vertically vto a plane determined by theperforation of the respective diaphragms I2, 32 and the lamps' ing setscrews 6 is provided to effect theI adjustment of the respectivediaphragms I1, 21 .as therebythe latter may be' mounted in a positioninclined relative tothe lspring axis with the result that errors dueto`inclination may in the course of practical application be reduce'd toa minimum. Finally, a supplementary adjustment 'may `be eected bydisplacement of the plane ca -m by shifting the point m, i. e. byvertical displacement of for instance the lamp 25 by shifting same inthe slot 22 oi.' its mounting.

What is claimed is:

1. A gravity meter comprising in combination a casing' for the meter, amass mounted within the meter casing for vertical displacement, springmeans balancing the gravity force of said mass, an optic-electric cellsystem for converting light variations into electric values, said systemincluding two cell units, a, ilrst light source emitting light towardsone cell unit, a second light source emitting light towards the othercell unit, a first diaphragm arranged in each oi the light paths, asecond diaphragm arranged in each of the-light ,paths and located infront of said first diaphragm, each diaphragm having apertures whichpermit light from the source associated therewith to pass therethroughtowards the cell unit associated with the diaphragm, means for mountingsaid first diaphragms whereby they are adjustablein a substantiallyvertical direction and are adjustably turnable about a substantiallyhorizontal axis, said secondl diaphragms being arranged to be displacedwith said mass in such manner that upon a displacement of the mass thequantity of Vlight reaching one of the cell lunits increases while theto said cell system to indicate the difference between the measuringvalues of said two`.units,'said two cell units being arranged backy toback. in

` spaced relation in the center ofthe meter casing,

said' meter casing being provided with openings, one for each lightsource, a separate lamp casing arranged: outside of the meter casingopposite each opening in the meter casing. and means for mounting one ofsaid light sources in each lamp casing whereby the light source issubstantially vertically displaceable relative to the first diaphragmassociated therewith.

2. A gravity meter comprising in combination .a casing for the meter, amass mounted within each diaphragm having apertures which permit' lightfrom the source associated therewith to pass therethrough towards thecell unit associated with the diaphragm; a support xed to the sides ofsaid meter casing, said cell units and the first diaphragms beingrigidly supported from said support in spaced relation, said cell unitsbeing located centrally of the, meter casing in back to back relationand one cell unit and one first .dia-v phragm being located on oppositesides of the axis Vof said spring means, second diaphragms being carriedby said mass iny such manner that upon a displacement of the mass thequantity of light means mounted on each frame for substantially verticaladjusting movement, an optic-electric cell system for converting lightvariations into electric values, said system including a cell unitcarried by each slide means, saidcell lunits being l arranged back toback, a diaphragm carried by each slide means, each diaphragm beingaligned with the light sensitive face of the cell unit on its respectiveslide and being spaced therefrom, a second pair of diaphragms rigidlysuspended from said mass for movement therewith, each second diaphragmbeing spaced from a first diaphragm reaching one of the cell unitsincreases while the quantity of light reaching the other cell unitclecreases, and 'indicating means operatively connected to said cellsystem to indicate the difference between the measuring values of saidtwo units.

3. A gravity meter comprising in combination a casing for the meter, a.spring suspended from the top of said casing,a mass suspended from saidspring, said spring balancing the gravity force of said mass, a supportwithin the casing, aL pair of frames extending substantially verticallyfrom said support, said frames being spaced apart and on opposite sidesof the axis of the spring., slide on the side of latter' away from itsassociated cell unit, a pair of light sources carried byl said metercasing, each light source aligned with a first and asecond diaphragm andemitting light towards the cell unit associated with such first andsecond diaphragm, and each diaphragm having apertures to 'permit-- lightfrom its respective light source to pass therethrough and onto the cellunit associated therewith, said second diaphragms being arranged to bedisplaced with saidmass in such manner that upon a displacement of themass the quantity of light reaching one of the cell units increaseswhile the quantity of light reaching the other cell unit decreases.

4. A gravity meter as claimed in claim 1 wherein said second diaphragmsare rigidly connected to said mass and means are provided for securingthe mass to the end of said spring means at a desired inclinationrelative to the axis of the spring means. l

5. In a gravity meter as claimed in claim 1, a clamping member fixed tothe end of said spring means,said clamping member having a sphericalshaped portion and said mass provided with a cup-shaped depression whichseats on the spherical portion of the clamping member, and diametricallyOpposed screws extending through said clamping member and engaged withsaid mass to connect the clamping member and mass together. f

ANTON GRAF.

